case when 条件1 and 条件2
then 条件成立业务语句
else 条件不成立业务语句
end
例子一
select
case when id>5
then '大数'
else '小数'
end as 'aaa'
from t_goods;
例子二 也可以用于update语句
<update id="updateGroupOrderAfterOrderExpired">
update t_group_order
set state= case when expire_time < now()
then '${@[email protected]}'
else state end
where id = #{groupOrderId} ;
</update>